How to get initial timestamp of a http request in golang?

Question

I am writing a golang program using revel framework, in which i need to check the initial timestamp of a http request.

I know how to do it in C# :

 HttpContextWrapper context = Request.Properties["MS_HttpContext"] as HttpContextWrapper;

DateTime t2 = context.Timestamp.ToUniversalTime();

Didn't get much how to do it in Go.

Answer 1

HttpContext class in .Net framework sets the timestamp when a request arrives at the server. You might as well store the timestamp in the first line of your request handler function.

Answer 2

The simplest thing to do is grab the current time within your handler.

type Handler struct {
}

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  rs := time.Now().UTC()

  //TODO: Use the time.
}

If you want to measure the time taken by all middleware preceding your handler, then you can update the Go context and place your middleware at the start of your middleware chain.

Here's an example of what that middleware might look like:

package timemiddleware

import (
    "context"
    "net/http"
    "time"
)

// New returns new middleware which tracks the time that a request started.
func New(next http.Handler) http.Handler {
    return handler{
        next: next,
    }
}

type key int

const id = key(1)

type handler struct {
    next http.Handler
}

func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    ctx := context.WithValue(r.Context(), id, time.Now().UTC())
    h.next.ServeHTTP(w, r.WithContext(ctx))
}

// GetTime returns time from the current request, where it has previously been added by the middleware.
func GetTime(r *http.Request) (t time.Time, ok bool) {
    v := r.Context().Value(id)
    t, ok = v.(time.Time)
    return
}

You'd use this as per this example:

package main

import (
    "fmt"
    "net/http"
    "time"

    "github.com/xxxxx/timemiddleware"
)

func main() {
    next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        time.Sleep(time.Second * 5)
        w.Write([]byte("Hello"))
        if t, ok := timemiddleware.GetTime(r); ok {
            fmt.Println(t)
            fmt.Println(time.Now().UTC())
        }
    })

    h := timemiddleware.New(next)
    fmt.Println(http.ListenAndServe("0.0.0.0:8080", h))
}